[semiconductor container that prevents crystalization on storage wafers/masks]

ABSTRACT

A semiconductor container molded from a plastic material containing silver that absorb sulfide to prevent crystal formation on masks/wafers carried in the enclosed storage space inside the semiconductor container during a photolithographic process under the radiation of a deep-ultraviolet light source. In an alternate form of the invention, the inside wall of the semiconductor container is coated with a layer of silver to absorb sulfide. In another alternate form of the present invention, blocks of silver are fixedly provided inside the semiconductor container to absorb sulfide in the enclosed storage space.

This application claims the priority benefit of Taiwan patent application number 093134016 filed on Nov. 8, 2004. BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor container for carrying wafers/masks and more particularly, to such a semiconductor container, which has silver directly added to the material or coated on the inside wall of the semiconductor container during fabrication of the semiconductor container, so that silver absorbs sulfide, preventing crystal formation on storage wafers/masks.

2. Description of the Related Art

IC (Integrated Circuit) is one of the most important elements that construct the so-called “third wave revolution” or “information revolution”. Computer, mobile phone, Internet, and LCD are important inventions of this digital era that greatly influence the living of human beings. Because IC chip has a wide application, it is used in a variety of electronic consumer products including computer and mobile phone. Following fast development of semiconductor technology, electronic products are designed to meet the requirements of modern electronic features such as light, thin, short, small, high speed, high frequency, high performance, and high precision. Heavy market demand for electronic products having modern electronic features promotes development of semiconductor technology towards this market trend. In consequence, investment in semiconductor industry keeps increasing in recent years. Every manufacturer is trying hard to create new technology in order to take the leading place in the market so as to enjoy huge commercial profit from the market. In order to survive from severe market competition, it is important to reduce the cost and improve the efficiency in this semiconductor field.

IC fabrication is an application of photolithography. This technique is to have an electronic circuit pattern on a mask reticle be projected onto a wafer by light. After developing and baking, a contracted circuit pattern is formed on the wafer. The wafer thus obtained is then processed through other posterior procedures such as wafer saw, die attach, wire bond, molding, . . . and etc. Therefore, reducing line width should be achieved by improving photolithographic process. A relatively smaller line-width CD value means a relative bigger number of transistors in a unit area, and the IC will have a relative stronger function, lower power consumption and lower cost. For example, when improved the manufacturing process of a 128 MB DRAM from 0.25 μm to 0.13 μm, the productivity for 8 inches wafer will be increased by 4 times, or the number of dies will not be significantly reduced when improved the production to 256 MB DRAM. This is the Moore's law that is the observation made in 1965 by Intel co-founder Gordon Moore that each new memory integrated circuit contained roughly twice as much capacity as its predecesoor, and each chip was released within 18-24 months of the previous chip.

Due to Moore's law, the successability of technical improvement toward smaller line width CD value is determined subject to photolithographic techniques, and scanner is the key implement. Currently, 248 nm deep-UV is intensively used for 0.11 μm photolithography. However, due to wavelength's sake, it is not possible to have the downward going line be in the way like 90 nm˜65 nm. Further, the use of 248 nm deep-UV for 0.11 μm lithography requires the so-called PSM (phase shift mask) reticle, which is made of molybdenum (MO) that is about 2-3 times over the price of chromium (Cr). In order to obtain a relatively smaller line width, the wavelength of the exposure machine should be relatively shorter. Therefore, 248 nm deep-ultraviolet light is intensively used to substitute for 365 nm ultraviolet. Recently, there are manufacturers studying the use of 193 nm deep-ultraviolet photoresist and light source of ultra short wave (Argon fluoride excimer laser to generate 193 nm deep-ultraviolet light) to improve lithographic process to the stage of 0.13 μm˜65 nm.

However, current semiconductor manufacturers commonly use SMIF system provided by Hewlett-packard for storing and transporting wafers/masks, i.e., the so-called closed transfer container. SMIF system is designed to reduce particle flux in storage and transport of semiconductor products during a semiconductor manufacturing process. This objective is achievable by: keeping the air proximity to the wafer or mask from change relative to the wafer or mask during storage and transport so as to prevent passing of particles from the surroundings into the air proximity to the wafer or mask. SMIF system uses a small amount of particle-free air to provide a clean environment for the object where the movement and flowing direction of the air and pollutant are well controlled. This measure greatly reduces the cost for clean room.

Before using 193 nm deep-UV to run a lithographic process, as shown in FIG. 1, mask reticle A and mask pellicle B are stored in an enclosed storage container D. When in use, mask reticle A and mask pellicle B are taken out of the enclosed storage container D and put in a mini-environment, and then radiated with 193 nm deep-UV. At this time, harmful crystals C are formed on the surface of mask reticle A and mask pellicle B (see FIG. 3). These crystals C lower the transmittance of mask reticle A and mask pellicle B, thereby resulting in distortion of the circuit pattern on mask reticle A or low yielding rate. Sometimes, the whole lot of wafers becomes unusable. This problem is indeed serious. This problem is also seen in the old manufacturing process with 365 nm ultraviolet light. However, because the old manufacturing process employs a relatively longer wavelength that has a relatively lower energy to provide a relatively lower capacity, the transparency of crystals formed on wafers after radiation is still high enough, and the problem of crystal formation on wafers during running of the old manufacturing process is never so serious to obstruct the product. According to experimentation, the transmittance of crystals formed on wafers after radiation with 365 nm ultraviolet light T=76.1%; the transmittance of crystals formed on wafers after radiation with 248 nm deep-UV T=29.2%, which is approximately the limit; the transmittance of crystals formed on wafers after radiation with 193 nm deep-UV T=13%, which is about the opaque status. If this problem is not settled, semiconductor manufacturing process will be limited to 0.11 μm, and the unit transistor capacity will not be doubled as within 18 months as expected subject to Moore's law.

In order to eliminate the problem of the formation of crystals on mask reticle A and mask pellicle B, the inventor of the present invention studied the formation of harmful crystals C. FIGS. 1 and 2 show a 193 nm deep-ultraviolet exposure bake process according to the prior art. According to Example I in FIG. 2, mask reticle A and mask pellicle B were kept in an enclosed storage container D at 40° C. for 3 days, and then mask reticle A and mask pellicle B were taken out of the storage container D and put in a mini-environment and radiated with 193 nm deep-UV, and crystals were found on the surface of mask reticle A and mask pellicle B. According to Example II in FIG. 2, mask reticle A was put in an enclosed plastic storage container D at 40° C. for 3 days, and then mask reticle A was taken out of the plastic storage container D and put in a mini-environment and radiated with 193 nm deep-UV, and crystals were found on the surface of mask reticle A. According to Example III in FIG. 2, mask reticle A and mask pellicle B were put in an enclosed stainless steel storage container D at 40° C. for 3 days, and then mask reticle A and mask pellicle B were taken out of the stainless steel storage container D and put in a mini-environment and radiated with 193 nm deep-UV, and no crystal C formation was seen on the surface of mask reticle A and mask pellicle B. This study shows crystal formation has a great concern with the storage container D.

According to study, we wound the reasons of crystal formation as follows.

According to analysis, the chemical formula of the crystals formed on mask reticle and mask pellicle is (NH₄)₂SO₄, mainly composed of (NH₄)⁺ and (SO₄)²⁻. During synthesis, there are important catalysts: (a) light source of short wavelength high energy, (b) organic or inorganic gas, (c) environment humility.

Either the use of KrF (Krypton fluoride) excimer laser to generate 248 nm deep-ultraviolet light or ArF (Argon fluoride) excimer laser to generate 193 nm deep-ultraviolet light, the narrow pulse light has a high energy that is continuously supplied during photolithography, which causes crystal formation upon its radiation on mask. It shows that the shorter the wavelength is, the higher the energy and the lower the transmittance of crystal will be.

Poor airtight status of the storage container allows passing of wet air (water molecule) from the outside clean room into the inside of the storage container to provide element requisite for its chemical reaction, and therefore crystals are formed on the surface of mask reticle and mask pellicle after removal from the storage container and radiation with 193 nm deep-UV.

The material of the storage container itself releases harmful gas that penetrates into the inside of mask pellicle, thereby causing formation of crystals on mask reticle and mask pellicle after removal from the storage container and radiation with 193 nm deep-UV.

Because the aluminum frame of mask pellicle is made of aluminum alloy treated with a sulfuric acid process, a big amount of sulphate ion SO₄ ²⁻ is left on the surface of the aluminum frame of mask pellicle, and the concentration of sulfur molecule in the enclosed space inside the storage container will be increased following evaporation of sulphate ion SO₄ ²⁻, thereby causing crystal formation on mask reticle and mask pellicle after removal of mask reticle and mask pellicle from the storage container and radiation of mask reticle and mask pellicle with 193 nm deep-UV.

SUMMARY OF THE INVENTION

The present invention has been accomplished under the circumstances in view. It is therefore the main object of the present invention to provide a semiconductor container, which absorbs sulfide, preventing crystal formation on storage wafers/masks. According to one embodiment of the present invention, power of silver is directly added to plastics to form a silver-contained plastic material for injection molding into the designed semiconductor container such that power of silver in the semiconductor container absorbs sulfide, preventing crystallization on storage wafers/masks. According to an alternate form of the present invention, the inside wall of the semiconductor container is directly coated with a layer of silver that absorbs sulfide, preventing crystallization on storage wafers/masks. According to another alternate form of the present invention, blocks of silver are fixedly provided inside the enclosed storage space of the semiconductor container for absorbing sulfide to prevent crystal formation on storage wafers/masks.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic drawing showing a 193 nm deep-ultraviolet exposure bake process according to the prior art (I).

FIG. 2 is a schematic drawing showing a 193 nm deep-ultraviolet exposure bake process according to the prior art (II).

FIG. 3 is a schematic drawing showing crystal formation on a photo mask.

FIG. 4 is a sectional view of a semiconductor container according to one embodiment of the present invention.

FIG. 5 is a sectional view of an alternate form of the semiconductor container according to the present invention.

FIG. 6 is a sectional view of another alternate form of the semiconductor container according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 4, a semiconductor container 1 in accordance with the present invention is shown comprising a container base 11, and a top cover 12 covering the container base 11 and defining with the container base 11 an enclosed storage space 13.

According to conventional techniques, the container base 11 and the top cover 12 are respectively molded from plastics that are high molecule polymers extracted from petroleum. However, plastic material contains sulfide 2. After injection molding of the container base 11 and the top cover 12, sulfide 2 will be continuously evaporated from the container base 11 and the top cover 12. According to the before-stated analysis, crystallized compound contains a big percentage of sulfide. In order to eliminate this problem, power of silver 3 is added to plastic material to form a silver contained plastic material that is used and injection-molded into the designed container base 11 and the top cover 12. Thus, power of silver 3 in the container base 11 and the top cover 12 absorbs sulfide 2 in the material, preventing evaporation of sulfide 2 into the enclosed storage space 13, and therefore the problem of crystallization on the surface of wafers/masks is completely eliminated. Preferably, the plastic material used is an anti-static plastic material.

FIG. 5 is a sectional view of an alternate form of the semiconductor container according to the present invention. According to this embodiment, the semiconductor container 1 is constructed subject to SMIF (Standard Mechanical Interface) definitions. In order to facilitate closing/opening of the top cover 12, the locking force that locks the top cover 12 to the container base 11 is limited. Further, because there is a manufacturing tolerance from deformation, the airtight condition of the enclosed will become worse with the use of the semiconductor container 1, and external sulfide 2 will permeate into the enclosed storage space 13 of the semiconductor container 1 gradually. Therefore, the invention has the inside wall of the semiconductor container 1 be coated with a layer of silver 3 that absorbs sulfide 2 in the enclosed storage space 13.

FIG. 6 is a sectional view of another alternate form of the semiconductor container according to the present invention. According to this embodiment, blocks of silver 3 are fixedly provided in the enclosed storage space 13 inside the semiconductor container 1 for absorbing sulfide 2.

Further, the semiconductor container 1 can be made of any of a variety of materials containing silver 3.

As indicated above, the technical features of the present invention to prevent crystallization on wafers/masks are as follows.

1. Power of silver can be added to plastics to form a silver-contained plastic material for injection-molding into the designed container base and top cover such that power of silver power in the semiconductor container formed of the container base and the top cover absorbs sulfide, preventing crystallization on storage wafers/masks.

2. The inside wall of the semiconductor container can be directly coated with a layer of silver to absorb sulfide, preventing crystallization on storage wafers/masks.

3. Blocks of silver may be fixedly provided inside the enclosed storage space of the semiconductor container to absorb sulfide, preventing crystal formation on storage wafers/masks.

A prototype of semiconductor container has been constructed with the features of FIGS. 4˜6. The semiconductor container functions smoothly to provide all of the features discussed earlier.

Although particular embodiments of the invention have been described in detail for purposes of illustration, various modifications and enhancements may be made without departing from the spirit and scope of the invention. Accordingly, the invention is not to be limited except as by the appended claims. 

1. A semiconductor container made of a plastic material containing power of silver that absorbs sulfide, preventing crystal formation on storage masks/wafers in an enclosed storage space defined in the semiconductor container during a photolithographic process under the radiation of a deep-ultraviolet light source.
 2. The semiconductor container as claimed in claim 1, which comprises a container base, and a top cover covering said container base and defining with said container base said enclosed storage space.
 3. The semiconductor container as claimed in claim 1, wherein said plastic material is an anti-static plastic material.
 4. A semiconductor container prevents crystal formation on storage masks/wafers in an enclosed storage space defined in the semiconductor container during a photolithographic process under the radiation of a deep-ultraviolet light source, wherein the semiconductor container has a silver coated on an inside wall thereof for absorbing sulfide in said enclosed storage space.
 5. The semiconductor container as claimed in claim 4, which comprises a container base, and a top cover covering said container base and defining with said container base said enclosed storage space.
 6. A semiconductor container that prevents crystal formation on storage masks/wafers in an enclosed storage space defined in the semiconductor container during a photolithographic process under the radiation of a deep-ultraviolet light source, wherein the semiconductor container comprising at least one block of silver fixedly provided inside said enclosed storage space for absorbing sulfide.
 7. The semiconductor container as claimed in claim 6, which is made of a material containing silver.
 8. The semiconductor container as claimed in claim 6, which comprises a container base, and a top cover covering said container base and defining with said container base said enclosed storage space. 